Porous film and lithium-ion battery

ABSTRACT

A porous film, including a binder and inorganic particles. The porous film includes pores formed by the binder. The pores at least include a part of the inorganic particles. The inorganic particles have particle sizes that Dv10 is in a range of 0.015 μm to 3 μm, Dv50 is in a range of 0.2 μm to 5 μm, and Dv90 is in a range of 1 μm to 10 μm. Dv10 of the inorganic particles is less than Dv50 of the inorganic particles, and Dv50 of the inorganic particles is less than Dv90 of the inorganic particles, and the inorganic particles have particle sizes that the ratio of Dv90 to Dv10 is in a range of 2 to 100.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. patentapplication Ser. No. 16/000,764, filed on Jun. 5, 2018, which claimspriority to Chinese Patent Application No. 201810322931.1 filed on Apr.11, 2018, the contents of which are incorporated by reference herein.

TECHNICAL FIELD

The present application relates to the field of energy storage devices,and in particular, to a porous film and a lithium-ion battery.

BACKGROUND

Non-aqueous secondary batteries, particularly lithium-ion batteries, arewidely used in portable electronic devices such as notebook computers,digital cameras, camcorders, and cellphones due to their high energydensity and good rate performance. In recent years, the application oflithium-ion batteries as the power supply for new energy vehicles isalso promoting the development of lithium-ion battery technology. In thecycle process of the lithium-ion battery, with the progress of chargingand discharging, a gap will be created between the electrode and theseparator, resulting in a reduction of the cycle capacity of thelithium-ion battery and thereby having an influence on its service life.Therefore, there is an urgent need for a technical solution to solve theproblem of the gap issue between the separator and the electrode so asto improve the service life of the lithium-ion battery.

SUMMARY OF THE APPLICATION

In order to solve the problem in the prior art, a porous film and alithium-ion battery are provided according to the present application.

According to a first aspect of the application, a porous film isprovided, including: a binder; and inorganic particles, wherein theporous film contains pores formed by the binder, the pores at leastincludes a part of the inorganic particles, and the average wallthickness between the pores is in a range of 20 nm to 500 nm.

In the porous film described above, the porous film has an average poresize of 0.3 μm to 20 μm.

In the porous film described above, the inorganic particles haveparticle sizes such that particle size having a volume accumulation of10% (Dv10) is in a range of 0.015 μm to 3 μm, particle size having avolume accumulation of 50% (Dv50) is in a range of 0.2 μm to 5 andparticle size having a volume accumulation of 90% (Dv90) is in a rangeof 1 μm to 10 μm. Particle size having a volume accumulation of 10%(Dv10) refers to particle sizes which reach 10% of the cumulative volumefrom the side of small particle size in the granularity distribution ona volume basis. Particle size having a volume accumulation of 50% (Dv50)refers to particle sizes which reach 50% of the cumulative volume fromthe side of small particle size in the granularity distribution on avolume basis. Particle size having a volume accumulation of 90% (Dv90)refers to particle sizes which reach 90% of the cumulative volume fromthe side of small particle size in the granularity distribution on avolume basis.

In the porous film described above, particle size having a volumeaccumulation of 10% (Dv10) is less than particle size having a volumeaccumulation of 50% (Dv50), and particle size having a volumeaccumulation of 50% (Dv50) is less than particle size having a volumeaccumulation of 90% (Dv90).

In the porous film described above, the particle sizes of the inorganicparticles satisfy that: the ratio of particle size having a volumeaccumulation of 90% (Dv90) to particle size having a volume accumulationof 10% (Dv10) is in a range of 2 to 100.

In the porous film described above, a pore size distribution coefficient(D) of the pores in the porous film is in a range of 1 to 5.

In the porous film described above, the inorganic particles are at leastone of alumina, silica, magnesia, titanium oxide, hafnium dioxide, tinoxide, cerium dioxide, nickel oxide, zirconia, zinc oxide, calciumoxide, boehmite, aluminum hydroxide, magnesium hydroxide, calciumhydroxide, and barium sulfate.

In the porous film described above, the binder is at least one ofpolyvinylidene fluoride, vinylidene fluoride-hexafluoropropylenecopolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid,polyacrylic acid salt, sodium carboxymethylcellulose,polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate,polytetrafluoroethylene and polyhexafluoropropylene.

In the porous film described above, the porous film has a porosity of20% to 90%, and the porous film has a thickness of 0.2 to 10 μm.

In the porous film described above, a volume ratio of the inorganicparticles to the binder is in a range of 0.2 to 3.0.

According to a second aspect of the application, a lithium-ion batteryis provided, including: a positive electrode; a negative electrode; aseparator arranged between the positive electrode and the negativeelectrode; and non-aqueous electrolyte; and a porous film, wherein theporous film is the porous film according to the first aspect of theapplication.

In the lithium-ion battery described above, the porous film is arrangedon a surface of at least one of the positive electrode, the negativeelectrode and the separator.

The porous film provided by the application has excellent adhesion, andmeanwhile the pore structure of the porous film can still be wellmaintained after being immersed in the electrolyte, thereby reducing theprobability of pore blockage of the porous film and enabling the porousfilm to have high ionic conductivity. Therefore, the rate performance ofthe lithium-ion battery is greatly improved, and the providedlithium-ion battery has excellent rate performance and cycleperformance.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

FIG. 1 is an electronic microscope image (1000 times magnification) ofthe pore structure of the lower surface (namely, the surface of theporous film away from the porous substrate) of the porous film accordingto example 3.

FIG. 2 is an electronic microscope image (5000 times magnification) ofthe pore structure of the lower surface of the porous film according toexample 3.

FIG. 3 is an electronic microscope image (1000 times magnification) ofthe pore structure of the lower surface of the porous film according tocomparative example 3.

DETAILED DESCRIPTION OF THE PREFERRED EXAMPLES

Exemplary examples will be described in details below. While theseexemplary examples may be implemented in various forms, the applicationshould not be construed as limited to the examples of the applicationset forth herein. Rather, these examples are provided with the purposeof making the disclosure of the application thorough and complete andfully conveying the scope of the application to those skilled in theart.

According to a first aspect of the present application, a porous film isprovided, including a binder and inorganic particles of differentparticle sizes, and the inorganic particles are fixed by the binder.Since the porous film includes the binder, the porous film has goodadhesion, which can prevent the porous film from detaching during theuse of the lithium-ion battery, and enables the lithium-ion battery tohave a high safety performance. Moreover, the average pore size of theporous film is larger and the pore sizes are distributed uniformly, sothat the porous film has good electrolyte diffusion and absorptioncapability and high ionic conductivity, the polarization reaction insidethe lithium-ion battery can be reduced, thereby improving the rateperformance of the lithium-ion battery. In addition, since the averagewall thickness between the adjacent pores in the porous film is low, thebinder (usually a polymer, for example, polyvinylidene fluoride) can beprevented from swelling in the electrolyte and blocking the pores of theporous film after the porous film is subjected to the soaking process inthe electrolyte during the preparation of the lithium-ion battery.Therefore, the pore structure in the porous film can be more retained,smoothness of the lithium ion transport channel is ensured, and thepolarization reaction inside the lithium-ion battery is reduced, therebythe rate performance of the lithium-ion battery can be further improved.In addition, due to the presence of inorganic particles in the porousfilm, the stability of the pore structure is enhanced. Therefore, thepore structure is not softened and closed after the soaking process inthe electrolyte and the high-temperature and high-pressure process inthe forming stage, the possibility of the pore structure beingcompressed and damaged is reduced, smoothness of the lithium iontransport channel is ensured, and the polarization reaction inside thelithium-ion battery is reduced, ensuring that the lithium-ion batteryhas a high rate performance.

In the porous film, inorganic particles are at least one of alumina,silica, magnesia, titanium oxide, hafnium dioxide, tin oxide, ceriumdioxide, zirconia, nickel oxide, zinc oxide, calcium oxide, boehmite,aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and bariumsulfate. The inorganic particles may contain polar functional groupsselected from a hydroxyl group. The surface of the inorganic particlescontaining polar functional groups is more easily combined with thenon-solvent (third solvent) in the coagulating solution described belowin the preparation process, which is advantageous for the diffusion ofthe third solvent into the porous film along the surface of theinorganic particles. Thus, large pore structures are formed in thevicinity of the inorganic particles, and the pore structures with largeaverage pore sizes and small average wall thickness between the adjacentpores are easily obtained.

The particle sizes of the inorganic particles satisfy that the particlesize having a volume accumulation of 10% (Dv10) is in a range of 0.015μm to 3 μm, the particle size having a volume accumulation of 50% (Dv50)is in a range of 0.2 μm to 5 μm, and the particle size having a volumeaccumulation of 90% (Dv90) is in a range of 1 μm to 10 μm. The particlesize (Dv10) having a volume accumulation of 10% refers to particle sizeswhich reach 10% of the cumulative volume from the side of small particlesize in the granularity distribution on a volume basis. The particlesize (Dv50) having a volume accumulation of 50% refers to particle sizeswhich reach 50% of the cumulative volume from the side of small particlesize in the granularity distribution on a volume basis. The particlesize (Dv90) having a volume accumulation of 90% refers to particle sizeswhich reach 90% of the cumulative volume from the side of small particlesize in the granularity distribution on a volume basis. For example, theinorganic particles having large particle sizes and a narrow peakdistribution are used, therefore the exchange speed between thenon-solvent (third solvent) in the coagulation solution and the organicsolvent (first solvent) in the coating solution can be increased duringthe formation of the porous film, and a porous film structure with alarger average pore size and smaller average wall thickness between theadjacent pores is formed. Within this range, if the particle sizes ofthe inorganic particles become smaller, the exchange speed between thenon-solvent (third solvent) in the coagulation solution and the organicsolvent (first solvent) in the coating solution is decreased during theformation of the porous film, the development of the pore structure isslower, the average pore size of the formed pore is decreased, and theaverage wall thickness between adjacent pores is increased. Conversely,if the particle sizes of the inorganic particles become larger, theexchange speed between the non-solvent (third solvent) in thecoagulation solution and the organic solvent (first solvent) in thecoating solution is increased, the development of the pore structure isfaster, the average pore size of the formed pore is increased, and theaverage wall thickness between adjacent pores is decreased. However, ifthe particle sizes of the inorganic particles are too small and arebeyond this range, the exchange between the non-solvent (third solvent)in the coagulation solution and the organic solvent (first solvent) inthe coating solution will be adversely affected, and it is difficult toform a pore with a large average pore size. If the particle sizes of theinorganic particles are too large and are beyond this range, the surfaceof the formed porous film is not uniform, the strength of the porousfilm is decreased, and the adhesion force of the porous film isdecreased.

In some examples, the inorganic particles have particle sizes such thatDv10 is in a range of 1.0 μm to 1.6 μm, Dv50 is in a range of 2.0 μm to2.6 μm, and Dv90 is in a range of 3.0 μm to 4.0 μm.

In the above-described porous film, the particle size distribution ofthe inorganic particles satisfies Dv90/Dv10=2˜100. If Dv90/Dv10 isgreater than 100, which will lead to the particle size distribution ofthe inorganic particles being too wide, the uniformity of the formedpores is poor, and polarization reactions will easily occur in thelithium-ion battery.

In the above-described porous film, the average wall thickness betweenadjacent pores is in a range of 20 nm to 500 nm, and the average poresize of the porous film is in a range of 0.3 μm to 20 μm. The averagepore size of the porous film according to the present application islarger, so that the porous film has good electrolyte diffusion andabsorption capability and high ionic conductivity, and the polarizationreaction inside the lithium-ion battery can be reduced, therebyimproving the rate performance of the lithium-ion battery. In addition,since the average wall thickness between adjacent pores in the porousfilm is low, the binder (typically a polymer, for example,polyvinylidene fluoride) can be prevented from swelling in theelectrolyte and blocking the pores of the porous film after the porousfilm is subject to a soaking process in the electrolyte during thepreparation of the lithium-ion battery. Therefore, the pore structure inthe porous film can be maintained, smoothness of the lithium iontransport channel is ensured and the polarization reaction inside thelithium-ion battery is reduced, the rate performance of the lithium-ionbattery can be further improved.

In the above-described porous film, the pore size distributioncoefficient D of the pores in the porous film is in a range of 1 to 5.R10 represents pore sizes which reach 10% of the cumulative pore sizesfrom the side of small pore size in the pore size distribution curve(the pore sizes of 10% of the pores are less than R10). R90 representspore sizes which reach 90% of the cumulative pore sizes from the side ofsmall pore size in the pore size distribution curve (the pore sizes of90% of the pores are less than R90). The pore size distributioncoefficient D is equal to R90/R10. The closer to 1 the pore sizedistribution coefficient D is, the more uniform the pore sizes in theporous film will be, and thus the porous film will have better rateperformance and cycle performance.

In the above-mentioned porous film, the porous film has a thickness of0.2 μm to 10 μm. If the thickness of the porous film is larger, the gaspermeability of the porous film becomes deteriorated, and the rateperformance of the lithium-ion battery is decreased. If the thickness ofthe porous film is smaller, the adhesive force of the porous film isreduced, and the porous film tends to fall off due to a poor adhesiveforce when applied in a lithium-ion battery, resulting in deterioratedsafety performance of the lithium-ion battery. In some examples, theporous film has a thickness of 1 μm to 3 μm.

In the above-described porous film, the porous film has a porosity of20% to 90%. In some examples, the porous film has a porosity of 40% to60%.

In the above-described porous film, the binder is at least one ofpolyvinylidene fluoride, vinylidene fluoride-hexafluoropropylenecopolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid,polyacrylic acid salt, sodium carboxymethylcellulose,polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate,polytetrafluoroethylene and polyhexafluoropropylene.

In the above-described porous film, the volume ratio of the inorganicparticles to the binder in the porous film is in a range of 0.2 to 3.0.If the volume ratio of them is lower than 0.2, the average pore size ofthe porous film is reduced, the porosity is decreased, and the rateperformance of the lithium-ion battery is deteriorated drastically. Ifthe volume ratio of them is greater than 3.0, the adhesive force of theporous film is reduced. When the porous film is applied to a lithium-ionbattery, the porous film tends to fall off due to poor adhesion,resulting in deteriorated safety performance of the lithium-ion battery.

According to a second aspect of the present application, a method forpreparing a porous film is provided, which is used for preparing theporous film according to the first aspect of the present application,including steps of: (1) mixing inorganic particles with a binder, andthen adding a first solvent and uniformly stirring the mixture to obtaina coating solution, wherein the binder is dissolved in the firstsolvent; (2) uniformly coating the coating solution on at least onesurface of a substrate to form a wet film; (3) immersing the substratewith the wet film into a coagulation solution for phase transformation,wherein the coagulation solution includes a second solvent and a thirdsolvent, and the second solvent and the third solvent are miscible witheach other; (4) performing a drying process after the phasetransformation is completed, to obtain the substrate whose surface isprovided with a porous film, wherein the average wall thickness betweenadjacent pores in the porous film is in a range of 20 nm to 500 nm, andthe average pore size of the porous film is not less than 0.3 μm.

The above-mentioned substrate may be one of a separator, a positiveelectrode, and a negative electrode.

In the above-described method for preparing the porous film, the porousfilm is prepared using the principle of phase transformation (i.e.,non-solvent induced phase separation, NIPS). In the coating solutionobtained in the step (1), the first solvent is oily, and the binder (forexample, polyvinylidene fluoride) may be dissolved in the first solvent.The third solvent contained in the coagulation solution in step (3) isone or more selected from deionized water, ethanol, propanol, acetone,dimethyl carbonate and diethyl carbonate, and the binder is insoluble inthe third solvent (for example, deionized water). Therefore, after thecoating solution is coated on the substrate and then immersed in thecoagulation solution, since the first solvent in the coating solution isextracted into the third solvent (for example, deionized water) in thecoagulation solution, the binder in the coating solution is coagulatedand separated out, thus forming a porous film.

In the above-described preparation method for the porous film, in step(1), the first solvent is at least one of N-methylpyrrolidone (NMP),dimethylacetamide (DMAC), dimethylformamide (DMF), triethyl phosphate(TEP), and dimethyl sulfoxide (DMSO). The porous film formed using NMPhas the largest average pore size and the highest porosity, the porousfilm formed using DMF has the smallest average pore size and the lowestporosity, and the porous film formed using DMAC has the average poresize and a porosity between that of the porous films formed using NMPand DMF respectively.

In the above-described method for preparing the porous film, the solidcontent of the coating solution in step (1) is in a range of 7% to 25%.Within this range, if the solid content of the coating solution isincreased, the viscosity of the coating solution is increased, theexchange speed between the third solvent in the coagulation solution andthe first solvent in the coating solution becomes lower, and both theaverage pore size and porosity of the formed porous film are decreased.Conversely, if the solid content of the coating solution is decreased,both the average pore size and porosity of the porous film areincreased. However, if the solid content of the coating solution is toohigh and is beyond this range, the porous film cannot meet therequirement of gas permeability, and the porous film cannot be used inthe lithium-ion battery; if the solid content of the coating solution istoo low and is below this range, the strength of the porous film isdecreased, and it is difficult to form a film on the surface of thesubstrate. In some examples, the coating solution has a solid content of10% to 20%.

In the above-described method for preparing the porous film, thetemperature of the coating solution in step (1) is in a range of 15degrees Celsius to 30 degrees Celsius. In some examples, the temperatureof the coating solution is in a range of 20 degrees Celsius to 25degrees Celsius.

In the above-described method for preparing the porous film, the coatingof the coating solution in step (2) may be performed using a commoncoating method, such as roll coating, a gas knife coating, rod coating,scraper coating, gravure coating, screen coating, die coating, microgravure coating, dip coating or the like. In some examples, the dipcoating method is selected as the coating method of the coatingsolution.

In the above-described preparation method, the second solvent in step(3) is one or more selected from N-methylpyrrolidone (NMP),dimethylacetamide (DMAC), dimethylformamide (DMF), triethyl phosphate(TEP), and dimethyl sulfoxide (DMSO). The second solvent in step (3) maybe the same as the first solvent added in step (1).

In the above-described preparation method, in step (3), the masspercentage of the second solvent in the coagulation solution is in arange of 20% to 60%. If the content of the second solvent in thecoagulation solution is decreased, it is advantageous for the increaseof the average pore size and porosity of the porous film. However, ifthe content of the second solvent is too low, a dense skin may be formedon the surface of the porous film which is away from the substrate,resulting in deteriorated gas permeability of the porous film. If thecontent of the second solvent is too high, a complete porous structurecannot be formed or the formed porous film has a very low average poresize and a high wall thickness. In some examples, the mass percentage ofthe second solvent in the coagulation solution is in a range of 30% to40%.

In the above-described method for preparing the porous film, thetemperature of the coagulation solution in step (3) is in a range of 15degrees Celsius to 30 degrees Celsius. In some examples, the temperatureof the coagulation solution is in a range of 20 degrees Celsius to 25degrees Celsius.

In the above-described method for preparing the porous film, in step(3), the period for phase transformation is in a range of 10 s to 90 s.In some examples, the period for phase transformation is in a range of20 s to 60 s.

In the above-described method for preparing the porous film, in step(4), the drying temperature is in a range of 60 degrees Celsius to 70degrees Celsius, and the drying period is less than 1 min.

According to a third aspect of the present application, a separatorincluding the porous film according to the first aspect of the presentapplication is provided.

The separator includes a porous substrate and a porous film. The porousfilm is arranged on the surface of the porous substrate. In theabove-described separator, there is no particular limitation on the typeof the porous substrate, and it may be selected as actually required.Specifically, the porous substrate is at least one of polyethylene film(PE), polypropylene film (PP), polyethylene/polypropylene dual-layerfilm (PE/PP), polypropylene/polyethylene/polypropylene three-layer film(PP/PE/PP), non-woven fabric, polyimide, polyacrylonitrile porous film(PAN), and glass fiber film.

A method for preparing the above-described separator is further providedaccording to the present application, which is used for preparing theseparator according to the third aspect of the present application, andwhich includes steps of: (1) mixing inorganic particles with a binder,and then adding a first solvent and uniformly stirring the mixture toobtain a coating solution, wherein the binder is dissolved in the firstsolvent; (2) uniformly coating the coating solution on a surface of theporous substrate (for example, polyethylene) to form a wet film; (3)immersing the porous substrate (for example, polyethylene) with the wetfilm into a coagulation solution for phase transformation, wherein thecoagulation solution includes a second solvent and a third solvent, andthe second solvent and the third solvent are miscible with each other;(4) performing a drying process after the phase transformation iscompleted to obtain a separator in which a porous film is arranged onthe surface of the porous substrate (for example, polyethylene), whereinthe average wall thickness between adjacent pores in the porous film isin a range of 20 nm to 500 nm, and the average pore size of the porousfilm is not less than 0.3 μm.

In the above-described method for preparing the separator, the parametersetting of the preparation process is consistent with that of thepreparation process of the porous film according to the second aspect ofthe present application, and only the substrate is changed to poroussubstrate.

According to a fourth aspect of the present application, an electrodeincluding the porous film according to the first aspect of the presentapplication is provided. The electrode includes a current collector andan active material layer. The active material layer is arranged on thesurface of the current collector, and the porous film is arranged on thesurface of the active material layer which is away from the currentcollector.

In the above-described electrode, the electrode may be either a positiveelectrode or a negative electrode, depending on the current collectorand the active material used. There is no particular limitation on thetype of the current collector, and it can be selected as actuallyrequired. Specifically, the current collector is at least one ofaluminum foil, copper foil, nickel foil, titanium foil, silver foil,nickel-copper alloy foil, aluminum-zirconium alloy foil, stainless steelfoil and graphene film.

A method for preparing an electrode is further provided according to theapplication, which is used for preparing the electrode according to thefourth aspect of the present application, including steps of: (1) mixinginorganic particles with a binder, and then adding a first solvent anduniformly stirring the mixture to obtain a coating solution, wherein thebinder is dissolved in the first solvent; (2) mixing an active material,a conductive agent and a binder, adding an organic solvent (such asN-methylpyrrolidone) into the mixture, uniformly stirring the mixtureunder the action of a vacuum stirrer to obtain an electrode slurry, anduniformly coating the electrode slurry on the current collector and thendrying to form an active material layer (electrode) on the currentcollector; (3) uniformly coating the coating solution on the surface ofthe electrode to form a wet film; (4) immersing the electrode with thewet film into a coagulation solution for phase transformation, whereinthe coagulation solution includes a second solvent and a third solvent,and the second solvent and the third solvent are miscible with eachother; (5) performing a drying process after the phase transformation toobtain an electrode whose surface is provided with a porous film,wherein the average wall thickness between adjacent pores in the porousfilm is in a range of 20 nm to 500 nm, and the average pore size of theporous film is not less than 0.3 μm. The electrode may be either apositive electrode or a negative electrode.

In the method for preparing the electrode described above, the parametersetting of the preparation process is consistent with that of thepreparation process of the porous film according to the second aspect ofthe present application.

According to a fifth aspect of the present application, a lithium-ionbattery is provided. The lithium-ion battery includes the separatoraccording to the third aspect of the present application, or includesthe electrode according to the fourth aspect of the present application,or includes both the separator according to the third aspect of thepresent application and the electrode according to the fourth aspect ofthe present application. The electrode may be either a positiveelectrode or a negative electrode.

In the above-described lithium-ion battery, the positive electrodeincludes a positive electrode material capable of intercalation anddeintercalation of lithium (Li) (hereinafter sometimes referred to as“positive electrode material capable of intercalation/deintercalation oflithium (Li)”). Examples of the positive electrode material capable ofintercalation/deintercalation of lithium (Li) may include one or more oflithium cobaltate, nickel cobalt lithium manganate, nickel cobaltlithium aluminate, lithium manganate, iron manganese lithium phosphate,lithium vanadium phosphate, lithium oxide vanadium phosphate, lithiumiron phosphate, lithium titanate, and lithium-rich manganese-basedmaterials.

In the above-mentioned positive electrode material, the chemical formulaof lithium cobaltate may be expressed as Li_(x)Co_(a)M1_(b)O_(2-c),wherein M1 represents at least one selected from the group consisting ofnickel (Ni), manganese (Mn), magnesium (Mg), aluminum (Al), boron (B),titanium (Ti), vanadium (V), chromium (Cr), ferrum (Fe), copper (Cu),zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr),tungsten (W), yttrium (Y), lanthanum (La), zirconium (Zr), and silicon(Si), and the values of x, a, b, and c are respectively within thefollowing ranges: 0.8≤x≤1.2, 0.8≤a≤1, 0≤b≤0.2, −0.1≤c≤0.2.

In the above-mentioned positive electrode material, the chemical formulaof nickel cobalt lithium manganate or nickel cobalt lithium aluminatemay be expressed as Li_(y)Ni_(d)M2_(e)O_(2-f), wherein M2 represents atleast one selected from the group consisting of cobalt (Co), manganese(Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium(V), chromium (Cr), ferrum (Fe), copper (Cu), zinc (Zn), molybdenum(Mo), tin (Sn), calcium (Ca), yttrium (Sr), tungsten (W), zirconium(Zr), and silicon (Si), and the values of y, d, e, and f arerespectively within the following ranges: 0.8≤y≤1.2, 0.3≤d≤0.98,0.02≤e≤0.7, −0.1≤f≤0.2.

In the above-mentioned positive electrode material, the chemical formulaof lithium manganate is expressed as Li_(z)Mn_(2-g)M3_(g)O_(4-h),wherein M3 represents at least one selected from the group consisting ofcobalt (Co), nickel (Ni), magnesium (Mg), aluminum (Al), boron (B),titanium (Ti), vanadium (V), chromium (Cr), ferrum (Fe), copper (Cu),zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), andtungsten (W), and the values of z, g and h are respectively within thefollowing ranges: 0.8≤z≤1.2, 0≤g<1.0, and −0.2≤h≤0.2.

The negative electrode includes a negative electrode material capable ofintercalation and deintercalation of lithium (Li) (hereinafter,sometimes referred to as “negative electrode material capable ofintercalation/deintercalation of lithium (Li)”). Examples of thenegative electrode material capable of intercalation/deintercalation oflithium (Li) may include a carbon material, a metal compound, an oxide,a sulfide, a nitride of lithium such as LiN₃, lithium metal, a metalwhich formed an alloy with lithium, and a polymer material. Examples ofcarbon materials may include low graphitized carbon, easily graphitizedcarbon, artificial graphite, natural graphite, mesocarbon microbeads,soft carbon, hard carbon, pyrolytic carbon, coke, glassy carbon, organicpolymer compound sintered body, carbon fiber and active carbon. Whereincoke may include pitch coke, needle coke, and petroleum coke. Theorganic polymer compound sintered body refers to materials obtained bycalcining a polymer material such as a phenol plastic or a furan resinat a suitable temperature and carbonizing them, and some of thesematerials are classified into low graphitized carbon or easilygraphitized carbon. Examples of polymeric materials may includepolyacetylene and polypyrrole.

Among these negative electrode materials capable ofintercalation/deintercalation of lithium (Li), further, materials whosecharge and discharge voltages are close to the charge and dischargevoltages of lithium metal are selected. This is because that the lowerthe charge and discharge voltages of the negative electrode materialare, the more easily the battery can have a higher energy density. Thecarbon material can be selected as the negative electrode material,since the crystal structure of the carbon material has only smallchanges during charging and discharging. Therefore, good cyclecharacteristics and high charge and discharge capacities can beobtained. In particular, graphite can be selected, since it can providea high electrochemical equivalent and energy density.

In addition, the negative electrode material capable ofintercalation/deintercalation of lithium (Li) may include elementallithium metal, metal elements and semi-metal elements capable of formingan alloy together with lithium (Li), alloys and compounds including suchelements, etc. In particular, they are used together with the carbonmaterial, since good cycle characteristics and high energy density canbe obtained in this case. In addition to alloys including two or moremetal elements, alloys used herein further include alloys including oneor more metal elements and one or more semi-metal elements. The alloysmay be in the following forms of solid solutions, eutectic crystals(eutectic mixtures), intermetallic compounds, and mixtures thereof.Examples of metal elements and semi-metal elements may include tin (Sn),lead (Pb), aluminum (Al), indium (In), silicon (Si), zinc (Zn), antimony(Sb), bismuth (Bi), cadmium (Cd), magnesium (Mg), boron (B), gallium(Ga), germanium (Ge), arsenic (As), silver (Ag), zirconium (Zr), yttrium(Y), and hafnium (Hf). Examples of the above-described alloys andcompounds may include a material expressed as a chemical formula:Ma_(s)Mb_(t)Li_(u) and a material expressed as a chemical formula:Ma_(p)Mc_(q)Md_(r). In these chemical formulas, Ma represents at leastone of metal elements and semi-metal elements capable of forming alloyswith lithium, Mb represents at least one of these metal elements andsemi-metal elements other than lithium and Ma, Mc represents at leastone of the non-metal elements, Md represents at least one of these metalelements and semi-metal elements other than Ma, and s, t, u, p, q, and rsatisfy s>0, t≥0, u≥0, p>0, q>0, and r≥0, respectively. In addition, aninorganic compound that does not include lithium (Li) may be used in thenegative electrode, such as MnO₂, V₂O₅, V₆O₁₃, NiS, and MoS.

The lithium-ion battery described above further includes an electrolyte,which may be one or more of a gel electrolyte, a solid electrolyte, andan liquid electrolyte. The liquid electrolyte includes a lithium saltand a non-aqueous solvent.

The lithium salt is at least one of LiPF₆, LiBF₄, LiAsF₆, LiClO₄,LiB(C₆H₅)₄, LiCH₃SO₃, LiCF₃SO₃, LiN(SO₂CF₃)₂, LiC(SO₂CF₃)₃, LiSiF₆,LiBOB, and lithium difluoborate. For example, LiPF₆ is used as a lithiumsalt, since it can provide high ionic conductivity and improve cycleperformance.

The non-aqueous solvent may be a carbonate compound, a carboxylic acidester compound, an ether compound, other organic solvents orcombinations thereof.

The carbonate compound may be a chain carbonate compound, a cycliccarbonate compound, a fluorinated carbonate compound or combinationsthereof.

Examples of chain carbonate compounds include diethyl carbonate (DEC),dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropylcarbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate(MEC) and combinations thereof. Examples of the cyclic carbonatecompounds include ethylene carbonate (EC), propylene carbonate (PC),butylene carbonate (BC), vinyl ethylene carbonate (VEC), andcombinations thereof. Examples of the fluorocarbonate compound includefluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate,1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate,1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethyl carbonate,1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylenecarbonate, 1,1,2-trifluoro-2-methylethyl carbonate, trifluoromethylethylene carbonate, and combinations thereof.

Examples of carboxylic acid ester compounds include methyl acetate,ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate,ethyl propionate, γ-butyrolactone, decanolactone, valerolactone,mevalonolactone, caprolactone, methyl formate, and combinations thereof.

Examples of ether compounds include dibutyl ether, tetraethylene glycoldimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane,1,2-diethoxyethane, ethoxy methoxy ethane, 2-methyltetrahydrofuran,tetrahydrofuran, and combinations thereof.

Examples of other organic solvents include dimethyl sulfoxide,1,2-dioxolane, sulfolane, methyl sulfolane,1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, formamide,dimethylformamide, acetonitrile, trimethyl phosphate, triethylphosphate, trioctyl phosphate, phosphate esters, and combinationsthereof.

The electrode assembly of the lithium-ion battery to which the porousfilm of the present application is applied includes not only a woundtype electrode assembly, but also a laminated (stacked) type electrodeassembly and a folded type electrode assembly.

The present application is further described in details with examplesbelow. It should be understood that these examples are only forillustrating the application but are not intended to limit the scope ofthe application. In the examples, only the case where the electrodeassembly of the lithium-ion battery is wound type is illustrated, butthe application is not limited thereto.

In the following examples, reagents, materials, and instruments used arecommercially available unless otherwise specified.

Example 1

(1) Preparation of Negative Electrode

The negative electrode active material (artificial graphite), the binder(styrene-butadiene rubber), and the conductive agent (conductive carbonblack (Super P)) are mixed uniformly with deionized water at a massratio of 92:3:5 to prepare a negative electrode slurry, then thenegative electrode slurry is coated uniformly on front and rear surfacesof the negative electrode current collector copper foil, then a negativeelectrode active material layer is formed by drying the coated negativeelectrode current collector copper foil at 85 degrees Celsius, followedby cold pressing, slitting and cutting processes and a negativeelectrode tab is welded so as to obtain a negative electrode.

(2) Preparation of Positive Electrode

The positive electrode active material (lithium cobaltate (LiCoO₂)), thebinder (polyvinylidene fluoride (PVDF)) and the conductive agent(conductive carbon black (Super P)) are dissolved in the solvent(N-methylpyrrolidone (NMP)) at a mass ratio of 97:1.5:1.5. A positiveelectrode slurry is prepared by stirring uniformly the mixture, then thepositive electrode slurry is coated uniformly on front and rear surfacesof the positive electrode current collector aluminum foil, then apositive electrode active material layer is formed by drying the coatedpositive electrode current collector aluminum foil at 85 degreesCelsius, followed by cold pressing, slitting and cutting processes and apositive electrode tab is welded so as to obtain a positive electrode.

(3) Preparation of Separator

Inorganic particles (boehmite) are mixed with the binder (polyvinylidenefluoride) at a volume ratio of 1.2, and then N-methylpyrrolidone (firstsolvent) is added and uniformly stirred to obtain a coating solution,wherein the coating solution has a solid content of 7%. The coatingsolution is coated onto a porous substrate (polyethylene) using the dipcoating method to form a wet film. The porous substrate (polyethylene)with a wet film is immersed in a coagulation solution containingdeionized water (third solvent) and N-methylpyrrolidone (NMP, secondsolvent) for phase transformation, wherein the mass percentage ofN-methylpyrrolidone (second solvent) in the coagulation solution is 40%,and the coating solution and the coagulation solution are at thetemperature of 25 degrees Celsius. After being immersed in thecoagulation solution for 30 seconds, the porous substrate (polyethylene)with a wet film is dried in an oven at 60 degrees Celsius to obtain aseparator with a porous film. The particle size distribution ofinorganic particles (boehmite) is such that Dv10 is 0.9 μm, Dv50 is 1.8μm and Dv90 is 3.0 μm.

(4) Preparation of Electrolyte

A solution prepared with lithium salt LiPF₆ and a non-aqueous organicsolvent (ethylene carbonate (EC): diethyl carbonate (DEC): ethyl methylcarbonate (EMC): vinylene carbonate (VC)=8:85:5:2, by mass ratio) at amass ratio of 8:92 is used as the electrolyte.

(5) Preparation of Lithium-Ion Battery

An electrode assembly is obtained by winding the positive electrode, theseparator and the negative electrode, and followed by packaging,injection of the electrolyte, forming, and suction molding processes areperformed to obtain the lithium-ion battery.

Example 2

In this example, the preparation methods for the negative electrode, thepositive electrode, the electrolyte, and the lithium-ion battery are thesame as the corresponding preparation methods described in Example 1.The preparation method of the separator is the same as that described inExample 1, except that the solid content of the coating solution is 10%.

Example 3

In this example, the preparation methods for the negative electrode, thepositive electrode, the electrolyte, and the lithium-ion battery are thesame as the corresponding preparation methods described in Example 1.The preparation method of the separator is the same as that described inExample 1, except that the solid content of the coating solution is 15%.

Example 4

In this example, the preparation methods for the negative electrode, thepositive electrode, the electrolyte, and the lithium-ion battery are thesame as the corresponding preparation methods described in Example 1.The preparation method of the separator is the same as that described inExample 1, except that the solid content of the coating solution is 20%.

Example 5

In this example, the preparation methods for the negative electrode, thepositive electrode, the electrolyte, and the lithium-ion battery are thesame as the corresponding preparation methods described in Example 1.The preparation method of the separator is the same as that described inExample 1, except that the solid content of the coating solution is 25%.

Example 6

In this example, the preparation methods for the negative electrode, thepositive electrode, the electrolyte, and the lithium-ion battery are thesame as the corresponding preparation methods described in Example 1.The preparation method of the separator is the same as that described inExample 1, except that the solid content of the coating solution is 15%,and dimethylacetamide (DMAC) is selected as the second solvent.

Example 7

In this example, the preparation methods for the negative electrode, thepositive electrode, the electrolyte, and the lithium-ion battery are thesame as the corresponding preparation methods described in Example 1.The preparation method of the separator is the same as that described inExample 1, except that the solid content of the coating solution is 15%,and dimethylformamide (DMF) is selected as the second solvent.

Example 8

In this example, the preparation methods for the negative electrode, thepositive electrode, the electrolyte, and the lithium-ion battery are thesame as the corresponding preparation methods described in Example 1.The preparation method of the separator is the same as that described inExample 1, except that the solid content of the coating solution is 15%,and the particle size distribution of inorganic particles (boehmite) isthat Dv10 is 0.015 μm, Dv50 is 0.2 μm and Dv90 is 1.5 μm.

Example 9

In this example, the preparation methods for the negative electrode, thepositive electrode, the electrolyte, and the lithium-ion battery are thesame as the corresponding preparation methods described in Example 1.The preparation method of the separator is the same as that described inExample 1, except that the solid content of the coating solution is 15%,and the particle size distribution of inorganic particles (boehmite) isthat Dv10 is 0.2 μm, Dv50 is 1.0 μm and Dv90 is 2.0 μm.

Example 10

In this example, the preparation methods for the negative electrode, thepositive electrode, the electrolyte, and the lithium-ion battery are thesame as the corresponding preparation methods described in Example 1.The preparation method of the separator is the same as that described inExample 1, except that the solid content of the coating solution is 15%,and the particle size distribution of inorganic particles (boehmite) isthat Dv10 is 1.6 μm, Dv50 is 2.6 μm and Dv90 is 4.6 μm.

Example 11

In this example, the preparation methods for the negative electrode, thepositive electrode, the electrolyte, and the lithium-ion battery are thesame as the corresponding preparation methods described in Example 1.The preparation method of the separator is the same as that described inExample 1, except that the solid content of the coating solution is 15%,and the particle size distribution of inorganic particles (boehmite) isthat Dv10 is 2.2 μm, Dv50 is 3.5 μm and Dv90 is 5.8 μm.

Example 12

In this example, the preparation methods for the negative electrode, thepositive electrode, the electrolyte, and the lithium-ion battery are thesame as the corresponding preparation methods described in Example 1.The preparation method of the separator is the same as that described inExample 1, except that the solid content of the coating solution is 15%,and the particle size distribution of inorganic particles (boehmite) isthat Dv10 is 3.0 μm, Dv50 is 5.0 μm and Dv90 is 10.0 μm.

Example 13

In this example, the preparation methods for the negative electrode, thepositive electrode, the electrolyte, and the lithium-ion battery are thesame as the corresponding preparation methods described in Example 1.The preparation method of the separator is the same as that described inExample 1, except that the solid content of the coating solution is 15%,and the mass percentage of N-methylpyrrolidone in the coagulationsolution is 20%.

Example 14

In this example, the preparation methods for the negative electrode, thepositive electrode, the electrolyte, and the lithium-ion battery are thesame as the corresponding preparation methods described in Example 1.The preparation method of the separator is the same as that described inExample 1, except that the solid content of the coating solution is 15%,and the mass percentage of N-methylpyrrolidone in the coagulationsolution is 60%.

Example 15

In this example, the preparation methods for the negative electrode, thepositive electrode, the electrolyte, and the lithium-ion battery are thesame as the corresponding preparation methods described in Example 1.The preparation method of the separator is the same as that described inExample 1, except that the solid content of the coating solution is 15%,alumina is selected as inorganic particles, and the particle sizedistribution of alumina particles is that Dv10 is 0.9 μm, Dv50 is 1.8 μmand Dv90 is 3.0 μm.

Example 16

In this example, the preparation methods for the negative electrode, thepositive electrode, the electrolyte, and the lithium-ion battery are thesame as the corresponding preparation methods described in Example 1.The preparation method of the separator is the same as that described inExample 1, except that the solid content of the coating solution is 15%,magnesium hydroxide is selected as inorganic particles, and the particlesize distribution of magnesium hydroxide particles is that Dv10 is 0.9μm, Dv50 is 1.8 μm and Dv90 is 3.0 μm.

Example 17

(1) Preparation of Negative Electrode

The negative electrode active material (artificial graphite), the binder(styrene-butadiene rubber), and the conductive agent (conductive carbonblack (Super P)) are mixed uniformly with deionized water at a massratio of 92:3:5 to prepare a negative slurry, then the negative slurryis coated uniformly on front and rear surfaces of the negative electrodecurrent collector copper foil, then a negative electrode active materiallayer is formed by drying the coated negative electrode currentcollector copper foil at 85 degrees Celsius, followed by cold pressing,slitting and cutting processes and a negative electrode tab is welded toobtain a negative electrode.

(2) Preparation of Positive Electrode

The positive electrode active material (lithium cobaltate (LiCoO₂)), thebinder (polyvinylidene fluoride (PVDF)), and the conductive agent(conductive carbon black (Super P)) are dissolved in the solvent(N-methylpyrrolidone (NMP)) at a mass ratio of 97:1.5:1.5. A positiveslurry is prepared by stirring uniformly the mixture, then the positiveslurry is coated uniformly on front and rear surfaces of the positiveelectrode current collector (aluminum foil), then a positive electrodeactive material layer is formed by drying the coated positive electrodecurrent collector aluminum foil at 85 degrees Celsius. Inorganicparticles (boehmite) are mixed with the binder PVDF at a volume ratio of1.2, and then N-methylpyrrolidone (first solvent) is added and uniformlystirred to obtain a coating solution, wherein the coating solution has asolid content of 15%. The coating solution is coated onto the positiveelectrode current collector on which a positive electrode activematerial layer is arranged by the dip coating method to form a wet film.The positive electrode current collector with a wet film is thenimmersed in a coagulation solution containing deionized water (thirdsolvent) and N-methylpyrrolidone (second solvent) for phasetransformation, wherein the mass percentage of N-methylpyrrolidone inthe coagulation solution is 40%, and the coating solution and thecoagulation solution are both at the temperature of 25 degrees Celsius.After being immersed in the coagulation solution for 30 seconds, thepositive electrode current collector with a wet film is dried in an ovenat 60 degrees Celsius, then cold pressing, slitting and cuttingprocesses are performed and a positive electrode tab is welded to obtaina positive electrode with a porous film. The particle size distributionof inorganic particles (boehmite) is such that Dv10 is 0.9 μm, Dv50 is1.8 μm and Dv90 is 3.0 μm.

(3) Preparation of Separator

A polyethylene porous substrate is used as a separator.

(4) Preparation of Electrolyte

A solution prepared with lithium salt LiPF₆ and a non-aqueous organicsolvent (ethylene carbonate (EC): diethyl carbonate (DEC): ethyl methylcarbonate (EMC): vinylene carbonate (VC)=8:85:5:2, by a mass ratio) at amass ratio of 8:92 is used as the electrolyte.

(5) Preparation of Lithium-Ion Battery

An electrode assembly is obtained by winding the positive electrode, theseparator and the negative electrode, and then packaging, injection ofthe electrolyte, forming, and suction molding processes are performed toobtain the lithium-ion battery.

Example 18

(1) Preparation of Negative Electrode

The negative electrode active material (artificial graphite), the binder(styrene-butadiene rubber), and the conductive agent (conductive carbonblack (Super P)) are mixed uniformly with the solvent(N-methylpyrrolidone (NMP)) at a mass ratio of 92:3:5 to prepare anegative slurry, then the negative slurry is coated uniformly on frontand rear surfaces of the negative electrode current collector (copperfoil), then a negative electrode active material layer is formed bydrying the coated negative electrode current collector copper foil at 85degrees Celsius. Inorganic particles (boehmite) are mixed with thebinder (PVDF) at a volume ratio of 1.2, and then N-methylpyrrolidone(first solvent) is added and uniformly stirred to obtain a coatingsolution, wherein the coating solution has a solid content of 15%. Thecoating solution is coated onto the negative electrode current collectoron which the negative electrode active material layer is provided by thedip coating method to form a wet film. The negative electrode currentcollector with a wet film is then immersed in a coagulation solutioncontaining deionized water (third solvent) and N-methylpyrrolidone(second solvent) for phase transformation, wherein the mass percentageof N-methylpyrrolidone in the coagulation solution is 40%, and thecoating solution and the coagulation solution are both at thetemperature of 25 degrees Celsius. After being immersed in thecoagulation solution for 30 seconds, the negative electrode currentcollector with a wet film is dried in an oven at 60 degrees Celsius, andthen cold pressing, slitting and cutting processes are performed and anegative electrode tab is welded to obtain a negative electrode. Theparticle size distribution of inorganic particles (boehmite) is suchthat Dv10 is 0.9 μm, Dv50 is 1.8 μm and Dv90 is 3.0 μm.

(2) Preparation of Positive Electrode

The positive electrode active material (lithium cobaltate (LiCoO₂)), thebinder (polyvinylidene fluoride (PVDF)), and the conductive agent(conductive carbon black (Super P)) are dissolved in the solvent(N-methylpyrrolidone (NMP)) at a mass ratio of 97:1.5:1.5. A positiveslurry is prepared by stirring uniformly the mixture, then the positiveslurry is coated uniformly on front and rear surfaces of the positiveelectrode current collector aluminum foil, then a positive electrodeactive material layer is formed by drying the coated positive electrodecurrent collector aluminum foil at 85 degrees Celsius, and then coldpressing, slitting and cutting processes are performed and a positiveelectrode tab is welded to obtain a positive electrode.

(3) Preparation of Separator

A polyethylene porous substrate is used as a separator.

(4) Preparation of Electrolyte

A solution prepared with lithium salt LiPF₆ and a non-aqueous organicsolvent (ethylene carbonate (EC): diethyl carbonate (DEC): ethyl methylcarbonate (EMC): vinylene carbonate (VC)=8:85:5:2, by a mass ratio) at amass ratio of 8:92 is used as the electrolyte.

(5) Preparation of Lithium-Ion Battery

An electrode assembly is obtained by winding the positive electrode, theseparator and the negative electrode, and packaging, injection of theelectrolyte, forming, and suction molding processes are performed toobtain the lithium-ion battery.

Example 19

(1) Preparation of Negative Electrode

The negative electrode active material (artificial graphite), the binder(styrene-butadiene rubber), and the conductive agent (conductive carbonblack (Super P)) are mixed uniformly with the solvent(N-methylpyrrolidone (NMP)) at a mass ratio of 92:3:5 to prepare anegative slurry, then the negative slurry is coated uniformly on frontand rear surfaces of the negative electrode current collector (copperfoil), then a negative electrode active material layer is formed bydrying the coated negative electrode current collector copper foil at 85degrees Celsius, then cold pressing, slitting and cutting processes areperformed and a negative electrode tab is welded to obtain a negativeelectrode.

(2) Preparation of Positive Electrode

The positive electrode active material (lithium cobaltate (LiCoO₂)), thebinder (polyvinylidene fluoride (PVDF)) and the conductive agent(conductive carbon black (Super P)) are dissolved in the solvent(N-methylpyrrolidone (NMP)) at a mass ratio of 97:1.5:1.5. A positiveslurry is prepared by stirring uniformly the mixture, then the positiveslurry is coated uniformly on front and rear surfaces of the positiveelectrode current collector aluminum foil, then a positive electrodeactive material layer is formed by drying the coated positive electrodecurrent collector aluminum foil at 85 degrees Celsius. Inorganicparticles (boehmite) are mixed with the binder (PVDF) at a volume ratioof 1.2, and then N-methylpyrrolidone (first solvent) is added anduniformly stirred to obtain a coating solution, wherein the coatingsolution has solid content of 15%. The coating solution is coated ontothe positive electrode current collector on which the positive electrodeactive material layer is provided by the dip coating method to form awet film. The positive electrode current collector with a wet film isthen immersed in a coagulation solution containing deionized water(third solvent) and N-methylpyrrolidone (second solvent) for phasetransformation, wherein the mass percentage of N-methylpyrrolidone inthe coagulation solution is 40%, and the coating solution and thecoagulation solution are both at the temperature of 25 degrees Celsius.After being immersed in the coagulation solution for 30 seconds, thepositive electrode current collector with a wet film is dried in an ovenat 60 degrees Celsius, and then cold pressing, slitting and cuttingprocesses are performed and a positive electrode tab is welded to obtaina positive electrode with a porous film. The particle size distributionof inorganic particles boehmite is such that Dv10 is 0.9 μm, Dv50 is 1.8μm and Dv90 is 3.0 μm.

(3) Preparation of Separator

Inorganic particles (boehmite) are mixed with the binder (PVDF) at avolume ratio of 1.2, and then N-methylpyrrolidone (first solvent) isadded and uniformly stirred to obtain a coating solution, wherein thecoating solution has a solid content of 15%. The coating solution iscoated onto a porous substrate (polyethylene) by the dip coating methodto form a wet film. The porous substrate (polyethylene) with a wet filmis immersed in a coagulation solution containing deionized water (thirdsolvent) and N-methylpyrrolidone (second solvent) for phasetransformation, wherein the mass percentage of N-methylpyrrolidone inthe coagulation solution is 40%, and the coating solution and thecoagulation solution are both at the temperature of 25 degrees Celsius.After being immersed in the coagulation solution for 30 seconds, theporous substrate (polyethylene) with a wet film is dried in an oven at60 degrees Celsius to obtain a separator with a porous film. Theparticle size distribution of inorganic particles (boehmite) is suchthat Dv10 is 0.9 μm, Dv50 is 1.8 μm and Dv90 is 3.0 μm.

(4) Preparation of Electrolyte

A solution prepared with lithium salt LiPF₆ and a non-aqueous organicsolvent (ethylene carbonate (EC): diethyl carbonate (DEC): ethyl methylcarbonate (EMC): vinylene carbonate (VC)=8:85:5:2, by a mass ratio) at amass ratio of 8:92 is used as the electrolyte.

(5) Preparation of Lithium-Ion Battery

An electrode assembly is obtained by winding the positive electrode, theseparator and the negative electrode, and then packaging, injection ofthe electrolyte, forming, and suction molding processes are performed toobtain the lithium-ion battery.

Example 20

(1) Preparation of Negative Electrode

The negative electrode active material (artificial graphite), the binder(styrene-butadiene rubber), and the conductive agent (conductive carbonblack (Super P)) are mixed uniformly with the solvent(N-methylpyrrolidone (NMP)) at a mass ratio of 92:3:5 to prepare anegative slurry, then the negative slurry is coated uniformly on frontand rear surfaces of the negative electrode current collector copperfoil, and then a negative electrode active material layer is formed bydrying the coated negative electrode current collector copper foil at 85degrees Celsius. Inorganic particles (boehmite) are mixed with thebinder (PVDF) at a volume ratio of 1.2, and then N-methylpyrrolidone(first solvent) is added and uniformly stirred to obtain a coatingsolution, wherein the coating solution has a solid content of 15%. Thecoating solution is coated onto the negative electrode current collectoron which the negative electrode active material layer is provided by thedip coating method to form a wet film. The negative electrode currentcollector with a wet film is immersed in a coagulation solutioncontaining deionized water (third solvent) and N-methylpyrrolidone(second solvent) for phase transformation, wherein the mass percentageof N-methylpyrrolidone in the coagulation solution is 40%, and thecoating solution and the coagulation solution are both at thetemperature of 25 degrees Celsius. After being immersed in thecoagulation solution for 30 seconds, the negative electrode currentcollector with a wet film is dried in an oven at 60 degrees Celsius,then cold pressing, slitting and cutting processes are performed and anegative electrode tab is welded to obtain a negative electrode with aporous film. The particle size distribution of inorganic particles(boehmite) is such that Dv10 is 0.9 μm, Dv50 is 1.8 μm and Dv90 is 3.0μm.

(2) Preparation of Positive Electrode

The positive electrode active material (lithium cobaltate (LiCoO₂)), thebinder (polyvinylidene fluoride (PVDF)), and the conductive agent(conductive carbon black (Super P)) are dissolved in the solvent(N-methylpyrrolidone (NMP)) at a mass ratio of 97:1.5:1.5. A positiveslurry is prepared by stirring uniformly the mixture, then the positiveslurry is coated uniformly on front and rear surfaces of the positiveelectrode current collector aluminum foil, then a positive electrodeactive material layer is formed by drying the coated positive electrodecurrent collector aluminum foil at 85 degrees Celsius, then coldpressing, slitting and cutting processes are performed and a positiveelectrode tab is welded to obtain a positive electrode.

(3) Preparation of Separator

Inorganic particles (boehmite) are mixed with the binder (PVDF) at avolume ratio of 1.2, and then N-methylpyrrolidone (first solvent) isadded and uniformly stirred to obtain a coating solution, wherein thecoating solution has a solid content of 15%. The coating solution iscoated onto a porous substrate (polyethylene) using the dip coatingmethod to form a wet film. The porous substrate (polyethylene) with awet film is immersed in a coagulation solution containing deionizedwater (third solvent) and N-methylpyrrolidone (second solvent) for phasetransformation, wherein the mass percentage of N-methylpyrrolidone inthe coagulation solution is 40%, and the coating solution and thecoagulation solution are both at the temperature of 25 degrees Celsius.After being immersed in the coagulation solution for 30 seconds, theporous substrate (polyethylene) with a wet film is dried in an oven at60 degrees Celsius to obtain a separator with a porous film. Theparticle size distribution of inorganic particles (boehmite) is suchthat Dv10 is 0.9 μm, Dv50 is 1.8 μm and Dv90 is 3.0 μm.

(4) Preparation of Electrolyte

A solution prepared with lithium salt LiPF₆ and a non-aqueous organicsolvent (ethylene carbonate (EC): diethyl carbonate (DEC): ethyl methylcarbonate (EMC): vinylene carbonate (VC)=8:85:5:2, by a mass ratio) at amass ratio of 8:92 is used as the electrolyte.

(5) Preparation of Lithium-Ion Battery

An electrode assembly is obtained by winding the positive electrode, theseparator and the negative electrode, and then packaging, injection ofthe electrolyte, forming, and suction molding processes are performed toobtain the lithium-ion battery.

Comparative Example 1

In this comparative example, the preparation methods for the negativeelectrode, the positive electrode, the electrolyte, and the lithium-ionbattery are the same as the corresponding preparation methods describedin Example 1.

The separator is prepared as follows.

The boehmite and polyvinylidene fluoride at a volume ratio of 1.2 areadded into deionized water and uniformly mixed to prepare a slurry, andthe solid content of the slurry is 45%. Then, the slurry is uniformlycoated onto front and rear surfaces of the porous substrate(polyethylene) using the micro gravure coating method to form a wetfilm. After the wet film is dried in an oven, a separator is obtained.The particle size distribution of inorganic particles (boehmite) is thatDv10 is 0.9 μm, Dv50 is 1.8 μm and Dv90 is 3.0 μm.

Comparative Example 2

In this comparative example, the preparation methods for the negativeelectrode, the positive electrode, the electrolyte, and the lithium-ionbattery are the same as the corresponding preparation methods describedin Example 1. The preparation method of the separator is the same asthat described in Example 1, except that the solid content of thecoating solution is 4%.

Comparative Example 3

In this example, the preparation methods for the negative electrode, thepositive electrode, the electrolyte, and the lithium-ion battery are thesame as the corresponding preparation methods described in Example 1.The preparation method of the separator is the same as that described inExample 1, except that the solid content of the coating solution is 30%.

Parameters of Examples 1-20 and comparative examples 1-3 are shown inTable 1 below.

TABLE 1 Solid Content of second content of solvent in Position of porousthe coating Inorganic particle/μm Second coagulation film solution TypeDv10 Dv50 Dv90 solvent solution Example 1 surfaces of separator  7%boehmite 0.9 1.8 3.0 NMP 40% Example 2 surfaces of separator 10%boehmite 0.9 1.8 3.0 NMP 40% Example 3 surfaces of separator 15%boehmite 0.9 1.8 3.0 NMP 40% Example 4 surfaces of separator 20%boehmite 0.9 1.8 3.0 NMP 40% Example 5 surfaces of separator 25%boehmite 0.9 1.8 3.0 NMP 40% Example 3 surfaces of separator 15%boehmite 0.9 1.8 3.0 NMP 40% Example 6 surfaces of separator 15%boehmite 0.9 1.8 3.0 DMAC 40% Example 7 surfaces of separator 15%boehmite 0.9 1.8 3.0 DMF 40% Example 8 surfaces of separator 15%boehmite 0.015 0.2 1.5 NMP 40% Example 9 surfaces of separator 15%boehmite 0.2 1.0 2.0 NMP 40% Example 3 surfaces of separator 15%boehmite 0.9 1.8 3.0 NMP 40% Example 10 surfaces of separator 15%boehmite 1.6 2.6 4.6 NMP 40% Example 11 surfaces of separator 15%boehmite 2.2 3.5 5.8 NMP 40% Example 12 surfaces of separator 15%boehmite 3.0 5.0 10.0 NMP 40% Example 13 surfaces of separator 15%boehmite 0.9 1.8 3.0 NMP 20% Example 3 surfaces of separator 15%boehmite 0.9 1.8 3.0 NMP 40% Example 14 surfaces of separator 15%boehmite 0.9 1.8 3.0 NMP 60% Example 15 surfaces of separator 15%alumina 0.9 1.8 3.0 NMP 40% Example 16 surfaces of separator 15%magnesium 0.9 1.8 3.0 NMP 40% hydroxide Example 3 surfaces of separator15% boehmite 0.9 1.8 3.0 NMP 40% Example 17 surfaces of positive 15%boehmite 0.9 1.8 3.0 NMP 40% electrode Example 18 surfaces of negative15% boehmite 0.9 1.8 3.0 NMP 40% electrode Example 19 surfaces ofseparator 15% boehmite 0.9 1.8 3.0 NMP 40% and positive electrodeExample 20 surfaces of separator 15% boehmite 0.9 1.8 3.0 NMP 40% andnegative electrode Comparative surfaces of separator / boehmite 0.9 1.83.0 / / Example 1 Comparative surfaces of separator  4% boehmite 0.9 1.83.0 NMP 40% Example 2 Comparative surfaces of separator 30% boehmite 0.91.8 3.0 NMP 40% Example 3

Performance Test

The performances of the porous film and the lithium-ion batteryincluding the porous film prepared in Examples 1-20 and comparativeexamples 1-3 are tested, and the test method is described as follows.

(1) Thickness Test of Porous Film

A separator sample or an electrode sample provided with a porous film isplaced on a thickness gauge (Model VL-50 LITEMATIC from Naitutoyocompany) using a 5 mm flat bottom probe with a speed of 50 mm/min and apressure of 0.01 N. Each separator sample or electrode sample providedwith the porous film is measured for 60 thickness points, and theaverage thickness is taken as the measured value. The thickness of theporous film is equal to the thickness of the separator or the electrodecoated with the porous film minus the thickness of the separator sampleor the electrode sample without the porous film. In a case that thereare two porous films, the thickness is divided by 2 to obtain thethickness of each porous layer.

(2) Gas Permeability Test of Porous Film

A 100 mm×100 mm separator sample provided with a porous film is cut andtested using a US Gurley 4110 N permeability tester with a test gas of100 cc, and the period that the test gas passes completely through theseparator provided with the porous film is recorded as a Gurley value.The Gurley value of the porous film is equal to the Gurley value of theseparator provided with the porous film minus the Gurley value of theseparator without the porous film (i.e., a pure porous substrate). In acase that the electrode includes a porous film, since the currentcollector itself is gas-tight, the gas permeability of the porous filmcannot be evaluated according to such a method.

(3) Porosity Test of Porous Film

The length, width, and thickness of a separator sample or an electrodesample provided with a porous film are measured, the thickness of theporous film is obtained using the above-described method, and theapparent volume V1 of the porous film is obtained through calculation.The true volume V20 of the separator sample or the electrode sampleprovided with the porous film is measured using a true density meter(AccuPyc II Model 1340 Gas Pycnometer, Micromeritics Company), and thetrue volume V0 of the separator sample or the electrode sample withoutthe porous film having the same area is measured. The true volume V2 ofthe porous film is equal to V20−V0, and the porosity of the porous filmis equal to 1−V2/V1.

(4) Average Pore Size Test of Porous Film

The area of the porous film that needs to be measured is observed usingthe Model Sigma-02-33 Scanning Electron Microscope from Zeiss, andimages are saved. The maximum diameter L1 in the transverse directionand the maximum diameter L2 in the longitudinal direction for each porein the images are measured, and the pore size of the pore is equal to(L1+L2)/2. Pore sizes of 200 adjacent pores are measured and an averagevalue thereof is taken as the average pore size of the porous film.

(5) Pore Size Distribution Coefficient Test of Porous Film

The area of the porous film that needs to be measured is observed usingthe Model Sigma-02-33 Scanning Electron Microscope from Zeiss, andimages are saved. Pore sizes of 200 adjacent pores are measured toobtain a pore size distribution curve. R10 represents pore sizes whichreach 10% of the cumulative pore sizes from the side of small pore sizein the pore size distribution curve (the pore sizes of 10% of the poresare less than R10). R90 represents pore sizes which reach 90% of thecumulative pore sizes from the side of small pore size in the pore sizedistribution curve (the pore sizes of 90% of the pores are less thanR90). The pore size distribution coefficient D is equal to R90/R10. Thecloser to 1 the pore size distribution coefficient D is, the moreuniform the pore sizes will be. The higher the pore size distributioncoefficient D is, the poorer the uniformity of the pore sizes will be.

(6) Average Wall Thickness Test Between Adjacent Pores in the PorousFilm

The area of the porous film that needs to be measured is observed usingthe Model Sigma-02-33 Scanning Electron Microscope from Zeiss, andimages are saved. The wall thicknesses between each two adjacent poresamong 200 adjacent pores are measured and an average value thereof istaken as the average wall thickness between adjacent pores in the porousfilm.

(7) Rate Performance Test of Lithium-Ion Battery

At 25 degrees Celsius, the lithium-ion battery is discharged to 3.0 V ata constant current of 0.2 C, rested for 10 minutes, then charged to 4.4Vat a constant current of 0.7 C, then charged to 0.02 C at a constantvoltage of 4.4 V, and rested for 10 min, and is further discharged at aconstant current of 0.2 C until the voltage is 3.0 V. The dischargecapacity at this point is measured and recorded as Q1. Then, thelithium-ion battery is charged to 4.4 Vat a constant current of 0.7 C,is then charged to 0.02 C at a constant voltage of 4.4 V, rested for 10minutes, then discharged at a constant current of 2 C until the voltageis 3.0 V. The discharge capacity at this point is measured and recordedas Q2.2 C/0.2 C rate performance (%) of the lithium-ion battery is equal toQ2/Q1×100%.

(8) Cycle Performance Test of Lithium-Ion Battery

At 25 degrees Celsius, the lithium-ion battery is charged to 4.4 V at aconstant current of 0.7 C, is then charged to 0.02 C at a constantvoltage of 4.4 V, rested for 10 minutes, is discharged to 3.0 V at aconstant current of 1 C, and rested for 10 minutes. The dischargecapacity at this point is measured and recorded as Q3. Theabove-described procedures are regarded as one cycle of charge anddischarge; 200 cycles are performed, and the discharge capacity afterthe 200 cycles is recorded as Q4.

The capacity retention rate (%) of the lithium-ion battery after 200cycles is equal to Q4/Q3×100%.

Test Results

The measured results of Examples 1-20 and comparative examples 1-3 areshown in Table 2 below.

TABLE 2 Porous film Average Pore size Average Gurley pore distributionwall Lithium-ion battery value Thickness size coefficient thickness RateCycle (s/100 cc) (μm) Porosity (μm) D (nm) performance performanceExample 1 24 2.4 58% 12 1.5 20 80.50% 86.70% Example 2 28 2.4 55% 7.82.1 90 84.20% 91.10% Example 3 32 2.4 53% 5 2.5 180 87.30% 95.30%Example 4 41 2.4 49% 3.6 3.6 320 83.90% 90.70% Example 5 55 2.4 46% 1.54.5 500 79.70% 85.30% Example 3 32 2.4 53% 5 2.5 180 87.30% 95.30%Example 6 35 2.4 52% 4.5 3 220 85.10% 92.30% Example 7 39 2.4 50% 3.73.2 300 82.90% 90.00% Example 8 45 2.4 48% 3.0 3.8 410 84.50% 91.50%Example 9 40 2.4 50% 4.0 3.4 320 85.40% 92.10% Example 3 32 2.4 53% 52.5 180 87.30% 95.30% Example 10 30 3.0 54% 5.5 2.2 160 86.30% 92.40%Example 11 28 4.0 55% 6.9 2.0 100 82.40% 89.80% Example 12 26 8.0 57%8.9 1.8 70 80.20% 86.50% Example 13 39 2.4 51% 8.1 3.6 50 82.20% 89.30%Example 3 32 2.4 53% 5 2.5 180 87.30% 95.30% Example 14 34 2.4 52% 3.52.3 300 84.10% 90.20% Example 15 43 2.4 49% 2.5 3.0 240 80.20% 85.20%Example 16 38 2.4 51% 3.1 2.9 230 85.20% 89.70% Example 3 32 2.4 53% 52.5 180 87.30% 95.30% Example 17 / 2.4 53% 4.9 2.6 180 86.90% 94.60%Example 18 / 2.4 53% 5.1 2.6 180 87.20% 94.90% Example 19 / 2.4 53% 4.92.7 180 85.50% 93.50% 32 2.4 53% 5 2.5 180 Example 20 / 2.4 53% 5.1 2.6180 85.70% 92.90% 32 2.4 53% 5 2.4 180 Example 1 36 2.4 46% / / / 68.80%70.10% Example 2 20 2.4 61% 18 1.3 12 73.70% 76.30% Example 3 91 2.4 42%0.5 5.3 600 72.70% 73.60%

As can be seen from the relevant data in Table 2 above, the porous filmaccording to the Examples of the present application has a higherporosity, and the lithium-ion battery has better rate performance andcycle performance.

As can be seen from the analysis of the relevant data of Examples 1-5and comparative examples 2-3, if the solid content of the coatingsolution is increased, the viscosity of the coating solution isincreased, the exchange speed between the non-solvent (third solvent) inthe coagulation solution and the organic solvent (first solvent) in thecoating solution becomes lower, the average pore size of the formedporous film is decreased, the average wall thickness between theadjacent pores is increased, the porosity of the porous film isdecreased, and the gas permeability of the porous film is deteriorated.However, if the solid content of the coating solution is too low (forexample, comparative example 2), it is difficult to form a porous film,and the electrochemical performance of the lithium-ion battery isdrastically degraded. The porous film in Example 3 has a larger averagepore size, uniform pore size distribution, and a small average wallthickness between adjacent pores. If the solid content of the coatingsolution is too high (for example, comparative example 3), the porosityof the porous film is too low and the gas permeability of the porousfilm is very poor. Referring to FIG. 3 , it can be seen that a smallpore size structure tends to be formed in the porous film, and theaverage wall thickness between the adjacent pores is large, whichseriously affects the cycle performance and rate performance of thelithium-ion battery.

As can be seen from the analysis of the relevant data of Example 3 andExamples 15 and 16, the rate performance and cycle performance of thelithium-ion battery is more significantly improved with the inorganicparticles containing polar functional groups. This is because thesurface of the inorganic particles containing polar functional groups ismore easily combined with the non-solvent (third solvent), i.e.,deionized water in the coagulating solution, which is advantageous forthe diffusion of the deionized water into the porous film along thesurface of the inorganic particles, and thus large pore structures areformed in the vicinity of the inorganic particles, and the porestructures with large average pore sizes and a small average wallthickness between the adjacent pores are easily obtained.

As can be seen from the analysis of the relevant data of Example 3,Example 6 and Example 7, if different organic solvents (second solvent)are selected, the pore structures in the obtained porous films are alsodifferent. The porous film formed with NMP has the largest average poresize and the highest porosity, the porous film formed with DMF has thesmallest average pore size and the lowest porosity, and the porous filmformed with DMAC has the average pore size and a porosity between thoseof the porous films formed with NMP and DMF respectively.

As can be seen from the analysis of the relevant data of Example 3 andExamples 8-12, the particle size of the inorganic particles has aneffect on the improvement of the rate performance and cycle performanceof the lithium-ion battery. If the particle size of the inorganicparticles is increased, the exchange speed between the non-solvent(third solvent) in the coagulation solution and the organic solvent(first solvent) in the coating solution is increased, the development ofthe pore structure is faster, the average pore size of the formed poreis increased, and the average wall thickness between adjacent pores isdecreased.

As can be seen from the analysis of the relevant data of Example 3 andExamples 13-14, the content of the organic solvent (second solvent) inthe coagulation solution has a great effect on the rate performance andcycle performance of the lithium-ion battery. If the content of theorganic solvent (second solvent) in the coagulation solution is reduced,the average pore size of the pores in the porous film is increased. Ascan be seen from the analysis of the relevant data of Example 1 andExamples 17-20, the porous film of the application may be formedseparately on the separator, the positive electrode, and the negativeelectrode, or may also be formed on both the separator and the positiveelectrode or formed on both the separator and the negative electrode.The lithium-ion battery has good rate performance and cyclingperformance in either case.

It should be understood by those skilled in the art that theabove-described Examples are only illustrative examples. Variouschanges, substitutions, and alterations could be made to the applicationwithout departing from the spirit and scope of the application.

What is claimed is:
 1. A porous film, comprising: a binder; andinorganic particles; wherein the porous film comprises pores formed bythe binder, the pores at least comprises a part of the inorganicparticles, wherein the inorganic particles have particle sizes that Dv10is in a range of 0.015 μm to 3 μm, Dv50 is in a range of 0.2 μm to 5 μm,and Dv90 is in a range of 1 μm to 10 μm; Dv10 of the inorganic particlesis less than Dv50 of the inorganic particles, and Dv50 of the inorganicparticles is less than Dv90 of the inorganic particles, and theinorganic particles have particle sizes that the ratio of Dv90 to Dv10is in a range of 2 to
 100. 2. The porous film according to claim 1,wherein the porous film has an average pore size of 0.3 μm to 20 μm. 3.The porous film according to claim 1, wherein the average wall thicknessbetween the pores is in a range of 20 nm to 500 nm.
 4. The porous filmaccording to claim 1, wherein a pore size distribution coefficient ofthe pores in the porous film is in a range of 1 to
 5. 5. The porous filmaccording to claim 1, wherein the inorganic particles are at least oneselected from the group consisting of alumina, silica, magnesia,titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickeloxide, zirconia, zinc oxide, calcium oxide, boehmite, aluminumhydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate.6. The porous film according to claim 1, wherein the binder is at leastone selected from the group consisting of polyvinylidene fluoride,vinylidene fluoride-hexafluoropropylene copolymer, polyamide,polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylic acidsalt, sodium carboxymethylcellulose, polyvinylpyrrolidone, polyvinylether, polymethyl methacrylate, polytetrafluoroethylene andpolyhexafluoropropylene.
 7. The porous film according to claim 1,wherein the porous film has a porosity of 20% to 90%.
 8. The porous filmaccording to claim 1, wherein the porous film has a thickness of 0.2 to10 μm.
 9. The porous film according to claim 1, wherein a volume ratioof the inorganic particles to the binder is in a range of 0.2 to 3.0.10. A lithium-ion battery, comprising: a positive electrode; a negativeelectrode; a separator, arranged between the positive electrode and thenegative electrode; non-aqueous electrolyte; and a porous film,comprising: a binder; and inorganic particles; wherein the porous filmcomprises pores formed by the binder, the pores at least comprises apart of the inorganic particles, wherein the inorganic particles haveparticle sizes that Dv10 is in a range of 0.015 μm to 3 μm, Dv50 is in arange of 0.2 μm to 5 μm, Dv90 is in a range of 1 μm to 10 μm; Dv10 ofthe inorganic particles is less than Dv50 of the inorganic particles,and Dv50 of the inorganic particles is less than Dv90 of the inorganicparticles; and the inorganic particles have particle sizes that theratio of Dv90 to Dv10 is in a range of 2 to
 100. 11. The lithium-ionbattery according to claim 10, wherein the porous film has an averagepore size of 0.3 μm to 20 μm.
 12. The lithium-ion battery according toclaim 10, wherein the average wall thickness between the pores is in arange of 20 nm to 500 nm.
 13. The lithium-ion battery according to claim10, wherein a pore size distribution coefficient of the pores in theporous film is in a range of 1 to
 5. 14. The lithium-ion batteryaccording to claim 10, wherein the inorganic particles are at least oneselected from the group consisting of alumina, silica, magnesia,titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickeloxide, zirconia, zinc oxide, calcium oxide, boehmite, aluminumhydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate.15. The lithium-ion battery according to claim 10, wherein the binder isat least one selected from the group consisting of polyvinylidenefluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide,polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylic acidsalt, sodium carboxymethylcellulose, polyvinylpyrrolidone, polyvinylether, polymethyl methacrylate, polytetrafluoroethylene andpolyhexafluoropropylene.
 16. The lithium-ion battery according to claim10, wherein the porous film has a porosity of 20% to 90%.
 17. Thelithium-ion battery according to claim 10, wherein the porous film has athickness of 0.2 to 10 μm.
 18. The lithium-ion battery according toclaim 10, wherein a volume ratio of the inorganic particles to thebinder is in a range of 0.2 to 3.0.
 19. The lithium-ion batteryaccording to claim 10, wherein the porous film is arranged on a surfaceof at least one selected from the group consisting of the positiveelectrode, the negative electrode and the separator.